ABSTRACT
Objective:To determine the phase-transition temperature of white vaseline produced by different processes by differen-tial scanning calorimetry ( DSC) in order to analyze the relevance between the melting point and the phase-transition temperature and the relevance between different production processes and the phase-transition temperature. Methods: Hermertic aluminum pans were used to encapsulate the samples, and the testing conditions were optimized. The sample weight was about 10 mg, and the range of measuring temperature was -20-100℃. The heating rate was 5℃·min-1 and the flow rate of nitrogen was 30 ml·min-1 . Results:The phase-transition temperature and the melting point were significantly different. The phase-transition temperature of white vaseline samples produced by different processes was quite different. Conclusion:Melting point determination in the current standard method of white vaseline exists defects, and the composition of white vaseline produced by various processes is quite different.
ABSTRACT
Objective: To determine the rheological properties of Dange ophthalmic in-situ gel and its common gel by using dynamic rheological experiments. Methods: Dange ophthalmic in-situ gel was prepared by adopting Poloxamer as thermosensitive material, and Dange gel was prepared by carbopol. Anton Paar MCR302 Rheometer was used to determine the rheological parameters of above two kinds of gel at different temperatures which speculated the phase transition time and gelling temperature of in-situ gel. Results: Dange ophthalmic in-situ gel was Newtonian liquid at low temperature, with its viscous modulus dominated. It was shear-thinning pseudoplastic fluid under the conditions of phase transition at room temperature, with its elastic modulus dominated. The phase transition temperature (Tg) was (24.4 ± 0.1)°C, and the gelling time was 9 s. Dange gel existed in network structure among a certain temperature range, it was stable and did not change with temperature. Conclusion: The test has established the rheological evaluation system of Dange ophthalmic in-situ gel or its common gel, accurately evaluated the rheological properties of the two gels by dynamic rheological parameters, and it can be used as the basis for the quality control of products.